1. Field of the Invention
The present invention relates to a polymer/ceramic composite paste for an embedded capacitor, and a method for fabricating an embedded capacitor using the composite paste. More particularly, the present invention relates to a polymer/ceramic composite paste for an embedded capacitor that has a high dielectric constant, which can be used for screen printing, and to a method for fabricating an embedded capacitor by screen printing.
2. Description of the Related Art
In recent years, there has been a growing interest in passive devices with high electrical performance for use in the manufacture of lightweight and compact electronic equipment. This is due to the fact that the number of passive devices used in electronic equipment is much greater than the number of active devices. For example, a portable mobile communication device has at least twenty times as many passive devices as active devices. Since many passive devices are currently mounted as discrete components on a surface of a substrate, they occupy a large area on the substrate, which results in a deterioration of the electrical performance, and in reliability problems with the final product.
An embedded passive (“integral passive”) device technique refers to removing discrete passive devices from the surface of the substrate, and then integrating the passive devices on one layer of a multilayer substrate. This integration makes it possible to decrease the area occupied by the passive devices, increase chip density, and shorten the interconnection length of the devices, thereby improving the electrical performance due to decreased parasitics.
Capacitors have been a focus of intense interest because they represent 40% (or more) of the passive devices. In particular, de-coupling capacitors and by-pass capacitors play a key role in electronics.
Since polymer/ceramic composites have superior processability inherent to polymers, and a high dielectric constant inherent to ceramics, they have drawn attention as prime candidate materials for embedded capacitors. The use of such materials enables formation of low-cost capacitors having a better performance at a temperature of up to 200° C. In particular, a number of studies on epoxy/ceramic composites are now being actively undertaken, regarding their compatibility with plastic printed circuit boards (PCBs) currently used in the industry.
Conventional embedded capacitors are fabricated by patterning an electrically conductive region for a bottom electrode on a substrate, forming a dielectric layer on the entire surface of the bottom electrode, and patterning an electrically conductive layer (for a top electrode) on the dielectric layer. However, this process has disadvantages, such as poor alignment between the top and bottom electrodes, and non-uniform thickness of the dielectric layer caused by the top and bottom electrodes. Further, if a high dielectric constant layer is formed on a region of the printed circuit board outside the region of a capacitor, capacitive parasitics adversely affect signal transmission.